The site is located about 800 feet north of the James River on the west side of US 301 (Belvidere Street). Several utilities and associated structures were present along the shoring line that had to be considered in the feasibility of the temporary shoring system. The soil profile consisted of 15 to 30 feet of fill followed by alluvial clays typically seen in the Richmond area. The fill was highly erratic with regard to soil type (sands, clays, debris) and stiffness (very soft to stiff). Bedrock was very deep and not an issue with regard to excavation or shoring installation. Groundwater was present near the bottom of the proposed excavation.

Subsurface provided design phase budgeting to the general contractor several times prior to the final bid phase. Subsurface had provided budgets assuming soldier piles with wood lagging and tie-back anchors. However, in an effort to reduce cost and construction time for the project, Subsurface proposed value engineered systems for the temporary shoring while providing the specified secant pile wall system required by the contract documents.

For the temporary shoring, Subsurface installed a hybrid system of pipe piles with wood lagging and a shotcrete soil nail wall along the north perimeter of the site where several utility lines were present. The hybrid system allowed us to cantilever the upper 5 to 8 feet of the excavation which allowed the drilled nails to start 8 to 10 feet below existing grade (below the utility elevations). Along the east and south perimeters, sloping was utilized to lower the top of shoring below utility elevations where a driven soil nail wall system was utilized

A design build permanent secant pile wall was called out on the structural drawings to support an existing museum and to reduce lateral earth pressure on the new foundation wall of the parking garage. Movement tolerances of the existing museum were limited to 1/2” vertical settlement, and ¼” horizontal movement during excavation and secant pile wall construction.

“Your entire team did a fantastic job. They were professional, team players, and willing to help develop solutions to problems. You could tell they wanted to turn over a quality project. It was a pleasure working with them.” Adam Britt, PE, Project Manager

Constructing a 957 bed 13-story tower in the center of the Duke University Hospital campus required significant excavation shoring closely coordinated with the myriad existing below grade utilities. Skanska hired Subsurface to design and install the ground shoring system. Subsurface proposed an anchored soldier pile wall to reduce the number of horizontal shoring elements that could conflict with existing utilities. The soldier piles were installed in pre-drilled holes and back filled with concrete. The holes were drilled using a Bauer foundation drill rig. Drilling to install soldier piles eliminates vibration and reduces noise versus driving piles into place. The anchors were attached to the wall using walers to allow for accurate anchor layout and in-field adjustments to avoid existing utilities.

Skanska, Calyx and the Duke Risk Mitigation team created a 3-D model of the proposed anchored soldier pile wall and existing utilities. TJ Ju, PE, Design Engineer along with Alex Smith, PE, Division Manager and Ben Possiel PE, Project Manager worked with Skanska and Calyx through multiple iterations of design in order to develop a shoring plan that would retain the deep cut while reducing the risk of utility damage.

Kelly Williams, Superintendent, used his 30 years of construction experience to install the shoring system, coordinate deliveries in the midst of an active hospital campus, and work closely with Skanska to complete the excavation shoring safely and on time.

Project Description

Subsurface Construction installed the first driven soil nail wall is allowed in Fairfax County, VA. L.F. Jennings (G.C.) selected Subsurface Construction to design and install the ground shoring system for the Freddie Mac Expansion project in McLean, VA. Fairfax County has a shoring geotechnical review board with strict guidelines for allowable soil properties used in shoring design. We were informed by the project geotechnical engineer that the review board never allows soil properties other than those stipulated by the board.

T.J. Ju, P.E., Chief Design Engineer at Subsurface, made a compelling argument by presenting verifiable historical data and research results to the review board and convinced them to allow alternative soil properties that more closely matched the existing subgrade conditions found on site.

In conjunction with this data, Subsurface developed a program to verify the assumed properties by testing the soil at every lift and sending data to the client. As a result, we were able to utilize our Driven Soil Nail System, developed by our company, which saved the owner time and money. By working in close conjunction with the grading contractor, we installed as much as 1,300 sq. ft. of shoring in a single day, and completed the shoring installation 2 weeks ahead of schedule.

Innovation is a hallmark of our company and we are pleased to be a part of this progression for soil nail wall design in Fairfax County, Virginia.

Project Description

The City Center is a 25-story mixed use project with two stories of below grade parking. The project is tightly nestled in an historic area of Durham. Excavation shoring was required to maintain streets on 3 sides of the excavation and historic brick buildings along one side. ­

Subsurface designed and constructed a mixture of anchored soldier pile walls and soil nail walls to allow for the deep excavation in a tight urban area. Anchored piles were used to control movement of the shoring system along the existing buildings and where existing utility locations would not allow for soil nailing. Soil nailing was used where feasible to lessen the overall cost of the shoring system.

Project Description

Waltonwood is an upscale senior living apartment complex built into a large hillside in an urban area. The client’s challenge was to cost effectively develop a difficult site that included a large retaining wall for parking and a building that would have soil pressure from a 26’ cut on only one side.

Subsurface designed a top-down permanent soil nail wall to allow for construction of the parking lot. Boulderscape then applied the aesthetic carved and stained shotcrete face to the site wall. For the building, the soil load on the structure was taken by a permanent soil nail wall, allowing the developer to construct the building without incurring the cost of a large concrete wall. The building wall was constructed inches in front of the permanent soil nail wall as though the building was constructed on a flat site.

Project Description

Duke Cancer Center is a state-of-the-art medical facility constructed in the heart of the Duke Hospital Campus. Excavation for the basement required shoring due to tight site constraints working around an existing facility, highly trafficked patient drop off, an adjacent ongoing construction project and numerous below grade utilities.

Subsurface designed and constructed a mixture of anchored soldier pile walls and soil nail walls to allow for the deep excavation in a highly congested hospital campus. We also used our driven soil nail system where feasible to reduce the overall shoring cost and duration.

Project Description

A major landslide forced the closure of the beautiful Blue Ridge Parkway near Deep Gap, NC. The road in the slide location was originally constructed on a deep embankment fill. The slope of the embankment fill varies, but averages 1.5(H):1(V) near the crest then gradually flattens to 2(H):1(V). Past roadway and drainage repairs attempted in the 1970’s, 1980’s, and again in the 1990’s were not successful long term. A permanent solution was needed.